Have someone watch you swing...sounds like your top hand is rolling over the top too soon and causing you to hit the top half of the ball...your swing should mimic the swing of an axe...if you allow the top hand to roll the blade before it hit the tree...it wont cut and it do hurt. Some questions though...
1. are you facing slower pitching than you usually see?
2. Have you switched to a lighter bat?
3. Have you seen a significant increase in your muscle build--weight training?